The present invention generally relates to vehicle braking and more particularly_relates to a process for generating defined actuating forces with respect to a brake that can be actuated electrically by means of an actuator and. a gear, wherein a first relationship exists between the actuator position and the actuator torque when the brakes are applied and a second relationship exists between the actuator position and the actuator torque when the brakes are released, as well as control systems for executing the process.
This type of process, for example, is known from the German utility model DE 296 22 787 U1. When the previously known process is executed, a characteristic curve which represents the relationship between the introduced motor current-to be supplied to the actuator and the actuating force that can be expected from this motor current is scanned by an electronic control device in such a way that the appropriate current value is allocated to the desired actuating force. Wheel sensors are used for determining the actual braking force value, wherein the characteristic curve can be changed so that the saved relationship between motor current and actuating force can be adapted to the actual relationship.
A particularly less advantageous aspect is that the signals of the wheel sensors which need to be used to execute the known process can be disturbed by drift and offset. For this reason, the previously known process is not reliable and its execution is difficult.
Thus, it is the object of the present invention to propose processes and control systems that will increase the functional reliability when executing the process and provide additional possibilities of generating defined actuating forces. In particular it should, however, be possible to execute the processes without using any sensors, since they are expensive and susceptible to faults.
This object is solved by the process under discussion in that the actuator torques resulting from the first as well as second relationships are evaluated in order to determine the efficiency.
So as to render the concept of the invention more concrete, the actuator torques are evaluated at the same actuator positions, preferably for determining an actuator torque value which should be applied at this actuator position when the efficiency xcex7=1.
In an advantageous further embodiment of the object of the invention the actuator torque is determined on the basis of the actuator current or the actuator current and the actuator voltage or the actuator current and the actuator position or the actuator voltage and the actuator position or the actuator current, the actuator voltage and the actuator position.
In addition, it is particularly advantageous when an estimate of the actuating force is determined on the basis of the actuator torque by means of the gear ratio.
According to another advantageous characteristic of the invention, the area for an actuator position region, which is limited by the two relationships, is evaluated to increase the quality of the process. For this purpose the evaluation is carried out in such a way that
a) the actuator torque value is calculated by working out the mean of the maximum and minimum actuator torque;
b) the actuator torque value is defined by calculating the ordinates of the horizontal straight line that cuts the area in half;
c) the mean of the actuator torques of the two relationships is worked out at the same actuator position and that a compensating straight line is established by means of the ensuing mean values, whose ordinates are used as an estimate for the actuator torque value;
d) the center of gravity of the area is calculated and its ordinates are used as an estimate of the actuator torque value.
An improvement of the targeted control is obtained through another advantageous characteristic of the invention, wherein the actuator torques are adjusted by the torques of inertia of the brake prior to determining the efficiency.
Moreover, it is particularly sensible if the brakexe2x80x94while it is being appliedxe2x80x94is additionally driven in such a way that an actuator torque-actuator position area is passed through, e.g. by superimposing a sinusoidal or cosine-shaped control signal over the actuating signal of the brake.
A first control circuit according to the present invention for executing the above-mentioned process is characterized in that
a) a position control device is provided, to which the control difference between the signals representing the desired actuator position and the actual actuator position respectively is supplied as the input signal and whose output signal is used to drive the actuator via an electronic energy unit;
b) a brake model adaptation module is provided, to which the actuator torque value corresponding to efficiency xcex7=1, the signals representing the appropriate actuator torques from one or both relationships and/or the signals representing the appropriate actuator position are supplied for adaptation and which generates model variables for a brake model;
c) a desired position value generator is connected upstream of the position control device, which contains the brake model and to which a signal corresponding to the desired actuating force as well as the adapted model variables are supplied and which generates the desired actuator position signal from the brake model;
d) an estimating module is provided, to which the signals corresponding to the actuator torque and/or the actuator position are supplied and which generates the actuator torque value corresponding to efficiency xcex7=1, the signals representing the appropriate actuator torques from one or both relationships and/or the appropriate actuator position.
A second control circuit according to the present invention for executing the above-described process is preferably characterized in that
a) a torque control device is provided, to which the control difference between a signal representing the desired actuator torque and a signal representing the actual actuator torque is supplied as the input signal and whose output signal is used to drive the actuator via an electronic energy unit;
b) a brake model adaptation module is provided, to which the actuator torque value corresponding to efficiency xcex7=1, the signals representing the appropriate actuator torques from one or both relationships and/or the signals representing the appropriate actuator position are supplied for adaptation and which generates model variables for a brake model;
c) a desired torque value generator is connected upstream of the torque control device, which contains the brake model and to which a signal corresponding to the desired actuating force as well as the adapted model variables are supplied and which generates the desired actuator torque signal from the brake model;
d) an estimating module is provided, to which the signals corresponding to the actuator torque and/or the actuator position are supplied and which generates the actuator torque corresponding to efficiency xcex7=1, the signals representing the appropriate actuator torques from one or both relationships and/or the appropriate actuator position.
In a third control circuit according to the present invention for executing the above-described process, the following components are provided:
a) an actuating force control device, to which the control difference between a signal representing the desired actuating force value and a signal representing the reconstructed actual actuating force value is supplied as the input signal and whose output signal is used to drive the actuator via an electronic energy unit;
b) a brake model adaptation module, to which the actuator torque value corresponding to efficiency xcex7=1, the signals representing the appropriate actuator torques from one or both relationships and/or the signals representing the appropriate actuator position are supplied for adaptation and which generates model variables for a brake model;
c) an actuating force reconstruction module that is connected upstream of the actuating force control device and to which the signals representing the actual actuator torque and/or the actual actuator position are supplied and which generates the actual actuating force value from the brake model;
d) an estimating module, to which the signals corresponding to the actuator torque and/or the actuator position are supplied and which generates the actuator torque corresponding to efficiency xcex7=1, the signals representing the appropriate actuator torques from one or both relationships and/or the appropriate actuator position.
In this connection it is particularly advantageous if the brake model adaptation module calculates the brake model variables by means of parameter estimates.
It is planned to have the brake model display the rigidity or efficiency of the brake in other advantageous embodiments of the object of the present invention.
A fourth control circuit according to the present invention for executing the above-described process exhibits the following circuit components:
a) a braking torque control device is provided, to which the control difference between a signal representing the desired braking torque value and a signal representing the reconstructed actual braking torque value is supplied as the input signal and whose output signal is used to drive the actuator via an electronic energy unit;
b) a characteristic curve adaptation module is provided, to which the estimated actuating force value and the signal corresponding to the wheel slip are supplied for adaptation and which generates parameters (characteristic values) for a relationship (characteristic curve) between the wheel slip and the braking torque;
c) a braking torque reconstruction module is connected upstream of the braking torque control device, which contains the relationship and to which a signal corresponding to the wheel slip as well as the adapted parameters (characteristic values) are supplied and which generates the actual braking torque value;
d) an estimating module is provided, to which the signals corresponding to the actuator torque and actuator position are supplied and which generates the estimated actuating force value.
A fifth control circuit according to the present invention to execute the above-described process is characterized in that
a) a slip control is provided, to which the control difference between a signal representing the desired wheel slip value and a signal representing the actual wheel slip value is supplied as the input value and whose output signal is used to drive the actuator via an electronic energy unit;
b) the estimated actuating force value and the signal corresponding to the wheel slip are supplied to a characteristic curve adaptation module for adaptation, which generates parameters (characteristic values) for a relationship (characteristic curve) between the wheel slip and the braking torque, wherein
c) a desired wheel slip value generator is connected upstream of the slip control, which contains the relationship and to which a signal corresponding to the desired braking torque as well as the adapted parameters (characteristic values) are supplied and which generates the desired wheel slip signal;
d) an estimating module, to which the signals corresponding to the actuator torque and the actuator position are supplied and which generates the estimated actuating force value.
In this connection it is particularly advantageous if the characteristic curve adaptation module adapts the characteristic curve by estimating the parameters.
Finally, the following circuit components are provided in a sixth control circuit according to the present invention for executing the above-described process:
a) an actuating force control device, to which the control difference between a signal representing the desired actuating force value and a signal representing the actual actuating force value is supplied as the input signal and whose output signal is used to drive the actuator via an electronic energy unit;
b) an actuating force sensor, whose output signal is the actual actuating force value; and
c) a monitoring module for the actuating force sensor, which monitors the actuating force sensor by means of the estimated actuating force value.